BME280函数没有库，但得到负数

Question

所以我正在使用 bme280 并尝试制作一个无需使用库即可读取温度的函数。但出于某种原因，它给了我 - 数字。有人知道为什么会这样吗？

 long BME280_ReadTemperature()
{
    long temperature = 0;
    Wire.beginTransmission(BME280_ADDR);
    Wire.write(BME280_TEMP_REG);
    Wire.endTransmission();

    //request 3 bits so that it can read 3 registers
    Wire.requestFrom(BME280_ADDR, 3);

    //These three are being read as shown in the powerpoint slides
    uint8_t reading1 = Wire.read();
    uint8_t reading2 = Wire.read();
    int reading3 = Wire.read();

    temperature |= (reading1 << 8);
    temperature |= (reading2 << 4);
    temperature |= reading3;

    return temperature;
}

Answer 1

取而代之的是 int in Arduino environment is 16-bit long. It is used for calculations of values with the size of int or below, but it is not sufficient to deal with 20-bit temperature value of BME280. You should use long，它是 32 位长。

而且移动量看起来不对。根据BME280数据表的5.4.8，位[3:0]存储在0xFC的高半部分，位[11:4]存储在0xFB，位[19:12]存储在 0xFA。偏移量应与这些匹配。

总之，行

    temperature |= (reading1 << 8);
    temperature |= (reading2 << 4);
    temperature |= reading3;

应该是：

    temperature |= ((long)reading1 << 12);
    temperature |= (reading2 << 4);
    temperature |= (reading3 >> 4);

BME280函数没有库，但得到负数

BME280 function without library, but getting negative numbers

c

arduino